diff --git a/rust/syn/ident.rs b/rust/syn/ident.rs
index 2c4b56505bec..03ccebf9c022 100644
--- a/rust/syn/ident.rs
+++ b/rust/syn/ident.rs
@@ -39,11 +39,11 @@ fn from(token: Token![_]) -> Ident {
 pub(crate) fn xid_ok(symbol: &str) -> bool {
     let mut chars = symbol.chars();
     let first = chars.next().unwrap();
-    if !(first == '_' || unicode_ident::is_xid_start(first)) {
+    if !(first == '_' || first.is_ascii_alphabetic()) {
         return false;
     }
     for ch in chars {
-        if !unicode_ident::is_xid_continue(ch) {
+        if !(ch == '_' || ch.is_ascii_alphanumeric()) {
             return false;
         }
     }